Publisher’s version / Version de l'éditeur:
Ottawa Construction News, 12, February 2, p. 8, 15, 2002-02-01
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
NRC Publications Archive
Archives des publications du CNRC
This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
A Seal in time: IRC launches new pavement crack-sealing consortium Bullis, R.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
NRC Publications Record / Notice d'Archives des publications de CNRC:
https://nrc-publications.canada.ca/eng/view/object/?id=25032b3e-013d-4354-9eb3-448f51eb787e https://publications-cnrc.canada.ca/fra/voir/objet/?id=25032b3e-013d-4354-9eb3-448f51eb787e
A Seal in time: IRC launches new pavement crack-sealing consortium
Bullis, R.
A version of this paper is published in / Une version de ce document se trouve dans: The Ottawa Construction News, v. 12, no. 2, February 2002, pp. 8, 15
www.nrc.ca/irc/ircpubs
A SEAL IN TIME:
IRC LAUNCHES NEW PAVEMENT CRACK-SEALING CONSORTIUM By Robert Bullis
More than two thirds of Canadian roads fall under municipal jurisdiction; of those, 90 percent are in need of immediate
repair, with costs estimated at $8.5 billion. The obvious way to slow road deterioration and maximize shrinking public funds is through preventive maintenance, but finding cost-effective ways of doing this requires research, and municipalities have neither the mandate nor the resources to fund such efforts.
However, when municipalities join consortium projects,
their smaller individual contributions can be levered to achieve significant results. The Urban Infrastructure Rehabilitation Program at the National Research Council’s Institute for
Research in Construction (IRC) has long been conducting
co-operative research projects that provide municipalities with the opportunity to gain this kind of leverage. A recent study on crack sealing conducted with the city of Montreal yielded some valuable information, which recently led to the launch of a new consortium project.
Cracking of asphalt is a recurring problem. Left
unchecked, cracks allow the infiltration of water, brine and debris into the pavement’s sub-structure, causing serious degradation and eventual pavement failure.
One of the most common techniques of preventive maintenance for asphalt roadways is to seal the cracks shortly after they occur. Effective sealing programs can increase pavement service life by 10-20 percent, and have the potential to save Canadian municipalities more than $800 million over the next 20 years.
But while it is cheaper to seal pavement cracks than it is to apply new asphalt, IRC research officer Dr. J-F. Masson says that crack sealants (which should provide six to twelve years of service life) are not presently meeting their full potential. In fact, sealants often fail within three years, mainly because of inappropriate selection and application.
In its publication, Effective Sealing of Pavement Cracks in
Cold Urban Environments, IRC tackled the problem of sealant
installation with a review of sealant performance fundamentals, common installation problems, and effective installation. IRC’s guide is now used throughout Canada, says Dr. Masson, but the challenges of road maintenance under Canadian conditions are ongoing – and so is the research at the IRC.
A recent joint project between IRC and the city of Montreal helped to identify material and installation problems with crack sealants. IRC researchers tested 12 commercially available
sealants to determine why they don’t live up to their expected life spans. They discovered that when sealants are kept at their recommended working temperature over the course of a day, they lose some of their performance characteristics. Heating a sealant to its working temperature and holding it there for even one hour can result in a degraded product. In addition,
sealants are often heated to temperatures above those
recommended by the manufacturer: first, because the melters that are used tend to overheat the sealant; and second, because crews sometimes overheat the product in order to make pouring easier.
Masson, who works at IRC’s laboratories on Montreal Road, says sealants need to be flexible at sub-zero temperatures. The Montreal study demonstrated that when a sealant is heated,
especially to higher temperatures, the components that provide the necessary flexibility can oxidize, evaporate or degrade. This results in the sealant losing some of its elastic
properties; therefore, the sealant can be in poor condition even before it’s applied to a crack.
But installation is still only half the necessary equation, and while the results of the Montreal study showed that
following a manufacturer’s suggestions is critical, the issue of sealant selection remains open.
“The next logical step,” says Dr. Masson, “is to develop guidelines for sealant selection – marking a significant shift in research that paves the way for the next 10 years in this field.”
SEALANT SELECTION – AN ONGOING CONCERN
In warmer climates, such as southern B.C., southern
Ontario, and the central U.S. states, sealants can provide good durability. However, sealants used in the repair of roads
subjected to arctic and sub-arctic climates must be able to endure unusual stresses. Low temperatures, such as those
occurring during a typical Canadian or northern U.S. winter, can make sealants inelastic so that they debond and no longer
tightly contact the walls of the crack. Hot-poured, bituminous sealants are generally selected according to empirical and
prescriptive standards, but those standards specify the best sealant only for average climate conditions, and not necessarily the best one for cold climates. No standards are available for the selection of high-performance sealants required for extended service life (up to 10 years).
The new consortium now being formed by IRC will examine ways to deal with the problems encountered in the Montreal study: inadequate standard specifications, and difficulty predicting sealant performance. Over the next several years, the consortium project will develop procedures to measure the aging effects of bituminous sealants; a method of assessing sealant performance; a sealant adhesion test that takes into account aggregate type; and performance guidelines for sealant selection.
The resulting performance-based guidelines, says Dr.
Masson, will substantially improve the performance of bituminous crack sealants in sub-zero temperatures. Because sealant
selection is based on solid scientific information and on local climate conditions, the guidelines will help users select
sealants based on specific local needs such as climate conditions and aggregate type. This means that premature
sealant failure will be minimized; durability and service life will be extended; the crack-sealing process will become more efficient; and sealant service life will be better estimated.
For municipalities, the guidelines will translate into better management of crack sealant programs, extended pavement service life, and decreased roadway maintenance costs. For sealant producers, improved quality control and better matching of products to specific conditions will result in less product
rejection; and increased use of crack sealing in road
maintenance will mean greater demand for sealant materials. Dr. Masson says the first meeting of the new consortium is scheduled for late February and includes major Canadian
municipalities, manufacturers, the Department of National Defence, and others responsible for large road networks.
For more information on the new consortium project, contact Dr. Masson at (613)993-2144, fax (613)952-8102, or email jean-francois.masson@nrc.ca.
____________________________________________ Robert Bullis is a freelance writer based in Ottawa.
